Spin Shortcut Key (2.8)
The shortcut has been removed in Blender 2.8. There are two ways you can add a shortcut, either through the keymap or by right clicking on the tool in the toolbar.

You can add it to your keymap under 3D View > Mesh as mesh.spin. However it's not particularly useful without the gizmo because the shortcut requires the configuration of the properties in the panel, which is much more time consuming.



The other approach is to right click on the spin tool in the toolbar, select Assign Shortcut and press the key combination that shall later trigger the tool. When you create the shortcut using this approach it will show the gizmo. This shortcut can also be created manually in the keymap (3D View > Mesh) by setting the identifier to wm.tool_set_by_id and the identifier of the tool to builtin.spin.